initialize a multidimensional C array of variable size to zero

Question

I want to initialize a two-dimensional array of variable size to zero. I know it can be done for a fixed-sized array:

int myarray[10][10] = {0};

but it is not working if I do this:

int i = 10;
int j = 10;
int myarray[i][j] = {0};

Is there a one-line way of doing this or do I have to loop over each member of the array?

Thanks

Answer 1

You cannot initialize it with an initializer, but you can memset() the array to 0.

#include <string.h>

int main(void) {
  int a = 13, b = 42;
  int m[a][b];
  memset(m, 0, sizeof m);
  return 0;
}

Note: this is C99. In C89 the declaration of m ( int m[a][b]; ) is an error.